Improved RA classification among early arthritis patients with the concordant presence of three RA autoantibodies: Analysis in two early arthritis clinics

Abstract

Background: The patients with RA benefit from early identification soon after the first clinical symptoms appear. The 2010 ACR/EULAR classification criteria were developed to fulfill this need and their application has been demonstrated to be effective. However, there is still room for improvement. Therefore, we aimed to evaluate the potential of the concordant presence of RF, anti-CCP and anti-carbamylated protein antibodies to improve current RA classification among early arthritis (EA) patients. Methods: Data from the first visit of 1057 patients in two EA prospective cohorts were used. The serological scores from the 2010 ACR/EULAR criteria and the concordant presence of the three RA autoantibodies were assessed relative to a gold standard consisting of the RA classification with the 1987 ACR criteria at the 2 years of follow-up. Results: The concordant presence of three antibodies showed predictive characteristics allowing for direct classification as RA (positive predictive value = 96.1% and OR = 80.9). They were significantly better than the corresponding to the high antibody titers defined as in the 2010 classification criteria (PPV = 88.8%, OR = 26.1). In addition, the concordant presence of two antibodies was also very informative (PPV = 82.3%, OR = 15.1). These results allowed devising a scoring system based only on antibody concordance that displayed similar overall performance as the serological scoring system of the 2010 criteria. However, the best classification was obtained combining the concordance and 2010 serological systems, a combination with a significant contribution from each of the two systems. Discussion: The concordant presence of RA autoantibodies showed an independent contribution to the classification of EA patients that permitted increased discrimination and precision.This work was supported by the Instituto de Salud Carlos III (Spain) through grants [PI17/01606 and RD16/0012/0014 to AG; RD16/0012/0011 to IG-A and RD16/0012/0012 to AB]. These grants are partially financed by the European Regional Development Fund of the EU (FEDER). CR was supported by Ministerio de Educacion Cultura y Deporte (Spain) through a FPU pre-doctoral fellowship [FPU15/03434]. LR-M was supported by a Xunta de Galicia predoctoral contract